Traditional blood collection continues to rely heavily on manual collection of whole blood from healthy donors through blood drives, from donor visits to blood centers or hospitals and the like. In typical manual collection, whole blood is collected by simply flowing it, under the force of gravity and venous pressure, from the vein of the donor into a collection container. The amount of whole blood drawn is typically a “unit,” which is about 450-500 ml.
More specifically, such a collection typically employs a pre-assembled arrangement of tubing and containers or bags, including a flexible plastic primary container or bag for receiving a unit of whole blood from a donor and one or more “satellite” containers or bags. The blood is first collected in the primary container, which also contains an anticoagulant (typically containing sodium citrate, phosphate and dextrose—often referred to as CPD). A preservative (often called an “additive solution” or AS, and commonly containing a saline, adenine, glucose, and mannitol or citrate and phosphate medium) may be included as part of a larger assembly of bags and tubes that are used in processing after the blood is collected.
After collection of a unit of whole blood, it is common practice in blood banking to transport the unit of whole blood, with connected tubing and containers, to a blood component processing laboratory, commonly referred to as a “back lab,” for further processing. Further processing usually entails manually loading the primary container and associated tubing and satellite containers into a centrifuge to separate the whole blood into components such as concentrated red cells and platelet-rich or platelet-poor plasma. These components are then manually expressed from the primary container into other pre-connected satellite containers, and may be again centrifuged to separate the platelets from plasma. Subsequently, the blood components may be leukoreduced by filtration for further processing or storage. In short, this process is time consuming, labor intensive, and subject to possible human error.
Another routine task performed by blood banks and transfusion center is “cell washing.” This may be performed to remove and/or replace the liquid medium (or a part thereof) in which the cells are suspended, to concentrate or further concentrate cells in a liquid medium, and/or to purify a cell suspension by the removal of unwanted cellular or other material.
Previous cell washing systems most typically involved centrifugation of a cell-suspension, decanting of the supernatant, re-suspension of concentrated cells in new media, and possible repetition of these steps until the cells of the suspension are provided at an adequately high or otherwise desirable concentration. Centrifugal separators used in the processing of blood and blood components have commonly been used in such cell-washing methods.
These processes are also quite time consuming, requiring repeated manual manipulation of the blood or blood components and assembly or disassembly of various fluid processing apparatus. This, of course, increases not only the costs, but the potential for human error or mistake. Accordingly, despite decades of advancement in blood separation devices and processes, there continues to be a desire for better and/or more efficient separation devices, systems and methods applicable to basic blood collection and processing modalities.
While many of the prior blood separation apparatus and procedures have employed centrifugal separation principles, there is another class of devices, based on the use of a membrane, that has been used for plasmapheresis, that is separating plasma from whole blood. More specifically, this type of device employs relatively rotating surfaces, at least one or which carries a porous membrane. Typically the device employs an outer stationary housing and an internal spinning rotor covered by a porous membrane.
One such well-known plasmapheresis device is the Autopheresis-C® separator sold by Fenwal, Inc. of Lake Zurich, Ill. A detailed description of a spinning membrane separator may be found in U.S. Pat. No. 5,194,145 to Schoendorfer, which is incorporated by reference herein. This patent describes a membrane-covered spinner having an interior collection system disposed within a stationary shell. Blood is fed into an annular space or gap between the spinner and the shell. The blood moves along the longitudinal axis of the shell toward an exit region, with plasma passing through the membrane and out of the shell into a collection bag. The remaining blood components, primarily red blood cells, platelets and white cells, move to the exit region between the spinner and the shell and then are typically returned to the donor.
Spinning membrane separators have been found to provide excellent plasma filtration rates, due primarily to the unique flow patterns (“Taylor vortices”) induced in the gap between the spinning membrane and the shell. The Taylor vortices help to keep the blood cells from depositing on and fouling or clogging the membrane.
While spinning membrane separators have been widely used for the collection of plasma, they have not typically been used for the collection of other blood components, specifically red blood cells. Spinning membrane separators also have not typically been used for cell washing. One example of a spinning membrane separator used in the washing of cells such as red blood cells is described in U.S. Pat. No. 5,053,121 which is also incorporated by reference in its entirety. However, the system described therein utilizes two separate spinners associated in series or in parallel to wash “shed” blood of a patient. Other descriptions of the use of spinning membrane separators for separation of blood or blood components may also be found in U.S. Pat. Nos. 5,376,263; 4,776,964; 4,753,729; 5,135,667 and 4,755,300.
RBC washing may be performed in order to reduce any residual plasma remaining in the product. Many transfusion-related reactions may be due to the plasma content of the transfused product. For example, Transfusion-Related Acute Lung Injury (TRALI) and other allergic reactions may occur in response to plasma content in a RBC product. Plasma also contains IgA, which is an antibody that may cause anaphylactic transfusion reactions in sensitive patients. Therefore, minimal plasma content within a RBC product may be desired.
Storage characteristics of the RBCs may also be affected by the plasma levels in a RBC product. When non-chloride storage solutions are used, a low extracellular chloride concentration generates a shift of the intracellular chloride ions out of the RBCs, leading to the movement of hydroxide ions into the RBCs, resulting in an increase in intracellular pH. Maintaining higher intracellular pH throughout storage is conducive to maintaining the RBCs' ATP and 2,3-DPG levels. ATP is a main source of energy for cell metabolism and function, while 2,3-DPG controls the movement of oxygen from red blood cells to body tissues and therefore is indicative of RBC health and functionality. Due to the fact that plasma normally has a chloride ion concentration of about 100 mM, reducing the plasma content of the RBC product reduces the chloride ion concentration of the supernatant which in turn may enhance the chloride/hydroxide ion shift between the RBCs and supernatant of the product, thus improving pH, ATP and 2,3-DPG storage parameters. Additionally, hypotonic additive solutions may reduce hemolysis levels during storage, so reducing the plasma content of the RBC product (thereby reducing the osmolality in the RBC product supernatant below ˜285 mOsm level of plasma) may be conducive to reducing hemolysis. A traditional washing procedure may occur several days after RBC separation and collection. During the waiting period before the washing procedure, intracellular pH may progressively decrease due to anaerobic cell metabolism. 2,3-DPG and ATP levels have been known to decrease during this period and may not be fully restored by a subsequent washing procedure several days later.
The subject matter disclosed herein provides further advances in membrane separators, potential cost reduction and various other advances and advantages over the prior manual collection and processing of blood.